Power transmission



Sept., 28, 1943. K. HEI-"EL POWER TRANSMISSION Filed Nov. 27, 1957 3 Sheets-Shee l fn i 1 i l I l l I i I HHH-IW ma 22 rmm Sept. 28, 1943. K. HEI-EL POWER TRANSMISSION 3 Sheets-Sheet 2 Filed Nov. 27, 1957 INVE NTOE s @h Wg Any `sepfn 28, 1943. K HEFEL 2,330,581

POWER TRANSMI S S ION FiledNov. 27, 1957 a sheets-sheet s Kewl Hegel lNVENToI. L @mwg Aww.

.lem forming the basis of;

Patented sept.v 2s, 1943 UNITEDSTATES PATENTS i` f Karl Betel,

, Application November 27, 1937, Serial v In Austria December 1i 1936",

e 1 Claim;

This inventionv'relat'es to a power transmission. Mechanisms are known which' eilectautom'atic changing in variable-speed gears vin dependence on the position of the accelerator of an' internalcombustion engine driving. the gear and on the magnitude of an output factor (speed nz or torque Mz) of the gear. With these mechanisms the driver always directly actuates only the fuel regulatingl member, while. the gear ratio isdetermined by the magnitude `of .theoutput factor and a member operated by thefaccelerator. The object of the present invention (which is kespecially applicable to gears of continuously l variable ratio) is to establish inthe engine, for

any desired power output-.only that operating basis of'thecharacteristic of the engin e.This

operating condition is characterised by aspeci'l vcally determined position ofthefuel-regulating member anda particular corresponding speed 'n1 (or torque M1) ofthe engine. Thisoperating condition must remain uninfiuenced by therunning resistance, that is theV arrangement-must be such that alterations in the, runningoesistance veffect such variations in the-transmission ratio that the speed n1 of the enginel remains unchanged as long asrthe engine powerfoutput control by direct operation ofuthe accelerator alone is insuicient overthe whole range of power.

output. Beyonda certain power the'most Verlicientoperating condition requires fullthrottle opening, further increase in power output .being obtainable only by raising the .'associatedspeed be obtained if ythe driver'` controls only.` the. ordinary accelerator.'v -Thus' previously knownfgar'- rangementsY are not capableof solving the probthe .present invention, because theydo not render theengne speedindependent of the running resistancev `and because the driver can inuence thegcontrol. of ,the gear ratio only by voluntary determination of theffuel supply; e

According to thepresent invention, on tlrieecoh-- trary,`there is provided a memberfor i selecting a desired effective (brake) power output lof the engine, which on the vone hand actuatestheuel supply member and brings this member falways into the position which for theselectedeiective power output gives theoptimum efiiciencyon l the basis of the engine vcharacteristic, (explained subsequently in i-connection with Fig. 1 ofthe accompanying drawings) thatvv determines -the most eilcient values; Voverthelwhole range-of;

Innsbruck, Austria; '.vestedVv inthey .l Alien'Property CustodialA l power'output, of 'the'iuel supply and speed of the engine, saidpower selecting vmember and an'- othermember controlled byA an output 'magnitude of the gearserving on the other'hand toactuate the adjusting and/or the indicating meansr for the gear ratioin such' a manner that ,the speed of the engine 'assumesgautomatically Ithe value for the selected power output that is the most -condition which is efficient when judged on the .is required to `remain constant. Furthermore,

However these operatingconditions cannot i vby 'an internal f gear.

eicient as determinedby thesaid vengine' charl acteristic.

Although the examples to ,be describedY relate mainly to conditions occurring in a vehicle driven combustion engine, the same'arrangement is applicable to many other like drives indifferent spheres'ofthe art.

An eiective controlis particularly convenl iently secured 'wherethe gear provides not-only f 'a sub-synchronous, but also' a super-synchronous l transmission to the driven shaft.

Although inthe course oi the present specification the speed takenas one voi" the two factors of regulationfor the transmission ratio itis tov be understoodthat in many cases the reciprocal value for the'torque of the driven 'shaft ght also be usedin a similar manner. 'I'hisjcourse howeveris more complicated and not always feasible. t Ijhe automatic ascertaining (adjusting) device according to the invention is directly applicable 30 to any type oftransmission gearing in which the changing over from` one transmission'ratio to another is electricallyinitiated"and vcarried out,

as also to every properly electric transmission The invention will now be rdescribed in greater detail, reference being had to the accompanying drawings comprising'graphs and diagrammatic representationsof examples'of the embodiment of theinvention; in which; v

` Fig. l shows graphically the dependence of the indicated output oan internal combustion engine on its speed atdifferent degrees of admission to the ,cylinders ofthe engine. Fig. 2 is a diagrammaticrepresentation ora device forv 1the` au`tomatic adjustment or indica-v tionofthe v most economical transmission ratio.

Fig. 3 shows diagrammatically another type of device forthe automatic indicationof the most economic transmission ratio.

Figs, 4, 5,-, and -6 show a detailcoiitact plate), l j Fig.Y "I a ycomplete lay-fout andFg. 8 an engine 'characteristic ,curve @similarvr to ,that shown in Referring `yto Fig. 1, Li denotes the ".indicated output?` of the internal combustion engine con- "nz ofthedriven vshaft is always rounding parts.

sidered, that is to say the quantity of fuel admitted to the engine in unit time, and n1 denotes the engine speed. In the following discussion the flow resistance and pressure drop in the gas ducts Vare neglected, in order to present the matter as simply as possible, since this discussion is required merely to explain the problem, which is not altered by taking these losses intoac'count. When these losses are neglected, the fuel admitted to the engine per hour (Li) increases in proportion to the speed n1. dicated outputs for various definite amounts of throttle opening can be represented respectively by straight lines O-A, O-B', O`-C, A, B, C' being considered as amounts of throttle opening grees of admission (throttle opening), for obtaining the effective output corresponding to the curve concerned. Now, if the maximum-eiciency points so obtained are connected together, there is obtained the dotted curve I-23-4A, which is the characteristic curve giving the most efficient values of fuel admission and speed m for the Wholerange of effective power output. If therefore maximum efficiency is to be obtained at different effective outputs the charge ;f and the speed m must be adjusted according to-the broken line I-V-2-3-4-A for instance if the characteristic ofv the engine is as shown in Fig. 1. This vmay .be achieved by appropriate selection ofthe. transmission ratio. This proper transmission ratio is automatically adjusted and/or indicatedin accordance with the invention for example by means of the following contrivance or arrangement.

In Fig. 2,` II Ydenotes a centrifugal governor .the speed of which is equal or proportional to the speed nz of the driven shaft. The governor II shifts the contact I2 towards the left `as the speed increases, with the result that this Icontact slides over a contact path 22-22 on the `Contact plate I3. The contact plate I3 is moved in` dependence on the setting of the regulatingv member by meansY of `which the internal combustion engine is controlled, namely ofthe throttle control or accelerator lever 21. This plate is ydivided up into mutually insulated areas I4, I5, I6, I1,` I8, and I9, the areal corresponding to the first gear ratio, area `I5 to the secondgear ratio, land so forth. From thecurrent collector a current circuit is closed in each case through the contact I2, the contact areaon which this contact bears for the time being, through the wire l?. I, the releasing relay 26 pertaining `to this area, and ground or the grounded mass of the sur- 'I'he relay 26 releases for operation the gear changing mechanism (which as being non-essential tothe presentinvention is not described in detail here) for the engaging of the required transmission ratio, or for the optical indication' of the ratio or speed `to be engaged by hand. In the case of electric transmission gears the required excitation for `the attainment of a certain transmission ratio may be directly adjusted by Vthe contact paths or areasId to I9. v I v ,AS -long as the setting of the accelerator'lever Accordingly the inr Ii I) 21 remains unchanged .the position of the contact plate I3 remains unchanged also. Thus on alteration of the speed nz'the contact I2 slides along. the line 22--22. The contact paths I4, I5, and so on are so distributed along this line 22-22 that the appropriate transmission ratios vary in inverse proportion to the speeds n2 of the driven shaft,` sov thatthe product of nzX re mains the same or is a constant magnitude. This constant is equal to the speed m of the That is to say, when the transmission ratio is actually adjusted according to this rule the driving speed m' remains constant, provided the charging of the engine, i. e. the setting of the throttle lever 21,. be also at the same time kept constant. It is` assumed for this purpose that the intervals between the ratios of which the gearing is capable are quite small; if these intervals are of considerable magnitude the gure for the driving speedfluctuates within certain limits about the constant value m obtained in the case of transmission gears with stepless alteration of' the transmission' ratio.v Alteration of the loadthus only brings about an' alteration of the specdnz of the driven shaft and of the transmission ratio between the driving `and the driven shaft; `The speed of the driving shaft, the charging of the engine; and therefore`also thev effective output of the engine remain constant.

The conditions on the line v22-'22 are intended to correspond for example to point I` in Fig. 1; If ank effective output corresponding to curve b-b in Fig. 1 is desired the poin`t`2 gives the most economical conditions for the attainment of this` output, that is to say both the charge f and also `the speed m must be appropriately increased as'comparedwith point I. The required increase in the chargingof the engine is obtained by further depressing the accelerator or throttle lever 21. This however at the same time causes the' contact plate I3`to be shifted downwards, so that now the line 23-23 is brushed by the contact I2 (Fig. 2) Along this' line the contact vpaths I4 to `I9 vare again required to be so distributed that the product of nzx is again equal rto a constant determined by thenew required speed n1 at the point 2 (Fig. l). In the same rmanner all, intermediate distributionsof the contact paths maybe determined'. A

From point 2 to point 3 in Fig.` 1 the-most economical conditions are obtainedbyA merely increasing the rate of charge of theengine while keeping the speed m constant. At the vpoint 3 the charging ofthe engine has attained its maximum.` The contact plate is then downwardly displaced to such an extent that the contact I2 `slides along the line 24-24. Since in this case the speed mhas no longer changed the distribution ofthe contact paths along the line 24-24 is the same afstha't along the line 23-23.

From point 3 to point `A in Fig. 1 the effective "output of the internal combustion engine is only altered by increasing the speed n1 while the charge f remains unaltered at its maximum value,

since on further depression of the throttle lever 21 the setting of the throttle valve 29 can not be altered any further, for instance owing to the provision of a stop (not shown in the drawings). The further movement of the lever 21 towards the carburetormay be assumed to be'taken up for example by a' spring 3U. On the other hand the contact plate I3 continues tobe" shifted downwards. For example 'the 'contact path '25-25 (Fig. 2) corresponds to the point 4 `in Fig. 1. The

arrangement the lever which therefco'a'cts ber 32, for instance an arm roller, which is pivotallyumounted on the rod 33. Y p The feelingmember is adjusted in an axial direcfavorable value for the mined; in accordance with the oharaoteristie of "the engine,` for each speed '11:2 and 'each degree for' charging f (Fig. 1), or represents some1 other function of the same capable or representation in the form `of a scale. In this `manner the most economical value l frende'red capable of beingdirectly read off on ther scale 36, and the justedby hand in accordance distributionr ofthe l:coritac-t paths is again'so de-j termined, 'as before, that the product ofv nzX remain'sfconst'an't, thenew `constant being given bythe" speed 11,1 required in the point 4. In this manner al1. other points upto' A are determined.

If the gear,changing beV effected as above de-V scribedfthere willcorrespond'to vany one setting of the Aaccelerator `or throttle lever 21 (in the case ofgearsjfth vsufficiently continuous change of transmission ratio)v a certain speed n1 andy a certain degreeof charging 'f ofthe engine. If'

the, proper angle y of ignition advance be also made dependent, on the settingof `the .regulating member .21 Aaiitorn'aticattainment of the most favorablfelworking conditions at any onemoment will thenb'gsecuredn Iftthetransinission ratio in 'a gearing be conf toiier/iitomatieany by o" device ofthe above describednature there may also with advantage be.previded a contrivancewhich allows of arbitrary interruption and reestablishing of the connection between the regulating member 21 and the throttle flap valve, 29, When this connection isinterrupted, depression i'fthe leverV 21 only effects shifting of thecontact plate I3 downwards, .While the throttlevalve remainsY in' the no-.lorad Irunningposition." Displacement of the plate I3 downwardsbrings about anfincrease in the enginespe'edm. relatively to the'spe'edjnz. This A th'us y`makes" it possible, in an ideally simple manner,` to brake the driven shaft .with the aid of the ,engineby mere operation of example; inlthe case of a. motor vehicle, the

entirelregulation'of output and. speed, including 5 braking, may be controlled.

1t 'is not essentiel' tothe rinvention that the adjustment, orjindication of the proper transrnission ratio be effected electrically. In Fig.,3 there is shown diagrammatieally a device'which indicates the `rnost economical transmission ratio 'ina purelyniechanical manner, so` that hand adjustment may'then beu effected accordingly. For thispurposetheres provided a roller 213| which is' rotated according to the setting of the 21, and with the surface of a feeling or scanning inemfurnished With a regulating member tion with respect togthe'roller by the centrifugal governor I I i'ndependence on the speed n2 oflthe driven `rshaft, `and lby a spring l34, against the roller. Rigidly connectedwith the feelingmem-rV ber 321s a pointer'frtiy which plays over a scale :36 mountedoh the rod 33.

Accordingto the deflection of the governor II orto ,the 'settingV oi."v the `regulating member 21,

l the roller. 32 bearsatfdiflerent points against the t surface oi the drum for the transmission ratio is gearingymay then be adwith this reading. A gearing controlled finv accordance with this invention acts as a perfect free-'Wheel gearing,"

21. Tlius with this 'one lever, fory transmissionA ratio deter- *equation* Fromme. 2 iixwili be eeen therme 'contact areas I'4-` I 9 are v gures of quite 'irregular configuration. If the arrangement be suchthat the contact is displaced proportionately to the speed ng jof the driyen shaft, and 'the' contact plate I3 displaced proportionately ,tojthe speed yof 'the driving shaft j (n1), thisbeing: perfectly possible according",to` what has bee'nsaidabove, since to each" setting of the acceleratorv or 'throttle' lever there corresponds a vdriving output and ydriving speed ni accurately determined by the characteristicKL of the engine, then the irregularlyshaped Y f;o1,f1ta .1et areas become resolved Ainto stripstcvon vergingritkowards the origin. l Tomakethis clear'aqtransmission gearis assumedV having nothingbut the ratios n1/nz=f=1/3,V1/2, 1", 2, 3

In this vcasel there is vobtained a contactarea as shown inFig'. 4,' in whichthe full lines 4I denote the' insulation strips, andthe chain-dotted lines v42' the" middle linesof the above-mentioned conf tactareas corresponding to the said transmission ratios.l vT vhelines42 are 'nothing else vbut the graphic representation of the function m--'Xnz Tina' system withtl'ie` axes n1 and 1ra-in `vvhich'it re1'ore'-sentsja. lstraight line converging to the ori- 4Vgin O. Inthis case thedisplacement of the contactAv or of the contact platef as shownn inflig, 2 in the directions -`of both"'axe`sis'proportional Eto 'the If these displacements be taken" proportional not 4tothe speeds themselves butt'o their logarithrns'th'erefis' obtained acontact plate asl-shown in 5,fsince the--relation` isnowjgiven by the los niiog izqlog mjj `which is represented in a system ,of "coordinates with logarithmic divisions byl parallelstraight Vlines,,43` inclin,ed at an angle of 45,a to.' the two axes, provided -.the standard for log mandlog nz l loe taken as the same; if the standard be different Vronly thee-angle of inclination alters. -CIThe'insulating strips are; omitted in Eig. 5.)y jIn order to obtain appropriate -conditions` the; contact plateA shown in `Fig.5 `rwould therefore have Vtoybedisplaced -vertiallyin dependence on lograr, and

.thecontact-(notshown) horizontally in depend- .:ence on 10s nz. y Y

. owing to' .thereon that the straight imesh run parallel lto each other there results a further simplication, inasmuch :as in kplace of the rmovement lin the two axial directions there isused the projection of`these movements on astraight line' at right angles to the lines 43. The contact plate 44 resulting frornso doing is shown in Fig. 6 in y`wll iicl;l 1`. the linesfj43again appear` as mid lines of contact areas separated from each other by insulat'iig strips 46.Y .This contactplate- M thus has nothingbut rectangular contactlareas 49v defined by the mid lines 43, and is y*moved to and r4iro ,by

lalinkfage 41.2independence on the v alue of'logm, while the contact I2 is mounted on`a linkagef48 provided'the construction of the gearing itseli allen i et auch line. difereniiatien in,V the transf,n missienfretie.

It thus. beeemes possible, for =.Xa1r1ple.in.V een; mestieri;witneleetrieeearsrwith the aid of cuite. simple apparatus, to varythe transmission ratio as finely graduatedlyw as desired, by} associating with each contact area. the. excitation appropriate tothe corresponding transmission ratio.

' i lig, 7 showsapparatus oi this descrip' l'.ion ,v for controlling the `.transrni,ssion ratioin dependence onthe ,Speeder thi-driven shaft on the. one, hand and, on the output.` adjusted for by. the setting ofY the` output regulating nuernberof the. driving meter; entheether hand- For this purpose there is. employed a ContactA plateM' .similar te that shownin Fig, 6 andr the` controllingof the plate 4.4? and, of the brushing contact I2 must accordingly be effected in dependence onthe value for log 11,1` and thaty forlog ne, respectively. The means employed for vthis purpose willl rst be described.

The accelerator or throttlev lever I rst of all shifts the rod 52 leading to the carburetor of the; drivingmotor 80, 'Ifheacceleratorflever 5I, which islengthened by the extension 53, is providedat its end with-a pin 54. The chanacteristic of; the.; driving motor is assumedas showninyFig.V 8 in which thecurve I, 2, 3, 4, 5.,A 6. represents.l the requisite -regulating curve to obtain maximum efficiency, analogously to Fig. 2.` With the degrecs` of charging of the engine corresponding tothe points I to 6 the pin 54 assumes the correspondingly numbered positions in Fig. '7; for which purpose the pin. 54 Works in the .slot 55 in the platei.v At the. same time the plate. 56 is rotated about its pivot, .and the rod 41, which is moved owing to engagement of a pin 59 attached .to this rod in a slot 6U in the-plate 56, and which carries the contact strip 44', carries out a longia tudi-nal movement. '.Ifhe guide slot- 55 ,in thepivoted plate 56 is .so dimensioned that thisrlongi.-

tudinal movement is proportional to the value for log n1. as is required for the proper actuation of the contactplate 44, for thereasons already explained. f Y

In asimilar manner the movement of the rod 48 may also be made tov depend on the shaft 6I driven with the speed n2 in dependence on the value for'log ne, through the intermediary of a centrifugal governor (compare governor IIin` Fig. 2). In accordance with the invention,"how

everyit' is also possible to dispense with ine- 'clianical operating means altogether, and' to move a rod or other element hydraulically from the driven shaft, according to any desired function, and more particularly accordingv to a loga-` rithmic function of the speed of rotation of the shaft, as is explained below. l

4'1"o the shaft 6I rotatingat speed ngthere 4is keyedan eccentric 62, so that the connecting rod 64 attached to the eccentric ring 63, and the pumppiston 65 carry out a strolreat each revolution of the shaft. By the actionV of the two non-returnvalves 66 and 66', Aliquid isv continuously delivered from the sump 61 into the cylind er 68 of the pump, and through the conduit 59 into a second cylinder 1I. In this latter there is fprovided a piston I3 which is longitudinally Inovable against the action of the spring "I2, and to which Ythere is connected a rod 48 carrying the contact I2. At intervals. alongthe walltof the .cylinder "are provided holes 'I5 the aperture of which may be varied in any suitable manner, for

`example by means of small screws (not shown `in Vthe drawings). u The` liquid `forced into.' thisv cylinder br the pump pistes.. 65. smits the pistas 1.3. towards.. trie. rient' te. site; an, extent .that the. maarl .of .liquiedeliverea attire.: .prev speed@ aanwinst flew haci? iste. the. sump .0.1. tl'neueh the parts. uneerered. by' theme11!! Pisis@ Bysjuitable. seleetieaarle ad'iustmentethe aver'- tures-` of.. the ports.; 15 it. ith, .,beeelmes.. passible, te impart te. theeentaet @the required. @rement effected in dependence enthe value fes les. InV order Steba able. te. eheelsthe amper.. flare: tienins Ofi thsxfapparatusatanr. time-@there naar further be. provided 111aee0rdaneewirithe lef vennen.. in the spa.. .etweeri their@ valves and 66. ef therme, ai Jr-nass l1; with. an. efi- J'ustable thrett1el8."th.raush Whl aeeraia per tionof the liquid delivered by pump is returnediritethe-semp 6.1.. since, th...disr1e.ea1.ent of 'the pistonred 48; that. is te r the .strate of this iroaisan accurate measure, ef. thespeecl ne; and therefore.' ia the. easefef. vehicles als@` a measure ef` the speed ef traveL, the meet ofthe. eisten. mai.'j be transmitted. te' die'at'elr. (net shewal 'marked 'efr fer eraelrle is kilemeters. per. heur.. If a.. eonvestieral. sreedf ometer (not sl1 yr12fA be'.V previdedadiaeleai this indicator, these. .tweifstruments 111.11512Y always yindicate the Samelsneed eff traYe1.-. These We instruments may also. be. eembinedyia. eee. and this Caseihe' twaineinters must remain. in register oreeineient with eaehether as lane. as the apparatus is in. arder. and. functioning. arene?- lyy., .If eheyeecingof. the. contact 1.2 ceases. te. .be

.aeeurately efreetede example-.amarte .Wear en I18` until the pointers.meveiareeister again. The

resuming arrangement then inpreper werking order..

If'th'e above. described. gear.' is.. eembined with the generallay-out shown in Figi? the followingresult is obtaineclV i The driving motor, for example` internal coinbustien eneine, drives, threugh they intermediary of.. the shaft emanating; was the. 'speed milan electric transmission gearZ of the type `which .consists of a `rnotorgenerator unit, and

vwhich acts in such. a manner thatv thealtering `of Vthe transmissionratio from subsynchronous run- Cning, through synchrcmized rumiillg,` t0 hypersynchronous running of the driven shaft 6I is eiected exclusively by altering the` neld excitation of the motor portion Of. the said unit., from a minimum positive value?, through zero, to a certain ncgativevalue.' Gear o f this kind isV devscribedv in `my `cofpending` application Serial Number 59,871. fThis alteringof `the excitation is eected bythe contact plate 44 and/oi` by the contact I2. .1 I i `The individual contact areason the plate 4.4 are bridged over` by resistances 85, QnlttheA area 86, which corresponds to zero excitation, has no conductive connection. The end contacts .are

connected bythe wires-81 and 81" to the slip rings 88 and 8 8. of the electric gear. Further, groin these slip rings wires 89 and 89' lead to contact Paths 90 and 9D' on which there brushes a brush 9| mounted `on the rod .48 and k'zonnectedl the wire s2 to ,the one pole 93 ofthe 'battery as. Thepole 93 is in its turn connected to contact paths 94 and 9.4'l `0n which the brushes. and

$5 mounted on the'rod 48 slide.` There -results the fellewllne mede efeperatiea.

As long as the contact i2 touches area on the right-hand side of the zero contact 88 on the contact plate 44 the current circuit is closed through 93', 94', 95', I2, possibly 85, l81', 88', exciter winding of the motor part of the gear unit, 88, 89', 9|, 92, 93. On relative movement of the contact I2 on the contact plate 44 towards the left the current becomes less and less owing to the additional connecting in of resistances 85, attains zero value on reaching the contact 86, and becomes reversed in direction after this contact has been passed over, since the current circuit is closed then through 93', 94, 95, l2, possibly 85, 81, 88, exciter winding, 88', 89, 90, 9|, 92, 93. The first mentioned current circuit corresponds to subsynchronous and the second to hypersynchronous running of the driven shaft 8l. Thus with a device of this description, the individual elements of which may of course be varied within wide limits, in conjunction with an electric transmission -gear unit of the type indicated, it is possible, by mere operation of the output control (accelerator pedal for instance in the case of motor vehicles), so to vary the transmission ratio, with suitable adaptation to the resistance encountered (resistance to propulsion in the case of automotive vehicles), that the driving motor always works with maximum efficiency.

Iclaim:

In a power transmission unit including an internal combustion engine, means controlling the supply of fuel to saidengine, a driven shaft, and a transmission gear with variable transmission ratio interposed between said driven shaft and said engine, the combination of a member for selecting any desired effective power output of the engine, said member being operatively connected with said fuel control means so as to effect correlated movements of said output selecting member and said fuel control means, two elements displaceable along a common path and being controlled by said power output selecting member and by an output magnitude of said gear, respectively, means whereby the element controlled by the output selecting member is displaced along said common path in proportion to the logarithms of the engine speed as said speed varies in accordance with the engine characteris-V tic determining, over the whole range of power output, the most efficient values of fuel supply and engine speed, and means whereby the element controlled by an output magnitude of said gear is displaced along said common path in propor tion to the logarithms of the speed of the driven shaft, said two elements'cooperating with one another for adjustment of the transmission ratio of said gear to maintain the speed of the engine, ir respectively of the resistance encountered by the driven shaft, at the value corresponding to the selected power output in accordance with said engine characteristic. f

KARL HEFEL. 

